The present embodiments relate to a device and method for registering medical image data.
Modern-day medical engineering technology provides a plurality of imaging modalities for visualizing regions of a body of a patient including internal tissue structures. Thus, for example, two-dimensional sectional images (slices) or three-dimensional volumetric images of regions of the body may be recorded using computed tomography (CT) or magnetic resonance tomography (MRT). When these technologies are used, acquired sets of image data may be compared with one another (e.g., the image data of the same patient acquired using different imaging techniques, image data of the patient with reference image data or image data of time series, of a beating heart, for example, or before and after therapeutic interventions).
Image registration methods are used in order to enable different image data of one or more patients to be displayed collectively and analyzed in a direct comparison. In the process, the image data to be compared is integrated and transformed into a common coordinate system. Where two image data sets are to be registered onto one another, one may be designated as a reference image R and the other as a model image M. The objective during the registration is to find the optimal transformation between the model image and the reference image. The optimal transformation may maximize a similarity metric of transformed model image and reference image. The optimization problem is solved using a registration algorithm.
The areas of application of automatic image registration encompass the combination of information from two or more imaging modalities for visualization or quantification, the combination of preoperative images with images acquired during an operation for the purpose of computer-assisted surgery, motion detection through registration of a time series of image data, automatic segmentation through registration onto pre-segmented anatomical atlases, and support for the planning of and treatment using radiotherapy. The requirements to be fulfilled by the registration algorithms are correspondingly diverse. In order to support robust automatic registration in clinical application, a registration algorithm specially tailored to the corresponding application is provided in conventional systems, the parameterization of the algorithm being defined for the specific registration problem. The registration functionality is accordingly specified for a specific organ, a specific anatomical structure or a specific region of the body, as well as for the specific registration problem (e.g., a specific imaging modality).
The application of a conventional registration method configured in this way to other than the explicitly specified registration problem and the specified image contents leads to a lack of robustness in the method as well as to a lack of precision in the registration and to misregistrations. Manually setting registration parameters in order to circumvent the problem may be out of the question, since setting by trial and error is very time-consuming and seldom leads to success. Often the clinical staff does not possess the technical knowledge to carry out such settings in relation to the registration algorithm.